The present disclosure relates to heart valve interventional systems and methods and more particularly, to mitral valve therapy systems and methods.
The long-term clinical effect of valve regurgitation is well recognized as a significant contributor to cardiovascular related morbidity and mortality. Thus, the primary goal of any therapy of the mitral valve is to significantly reduce or eliminate the regurgitation. By eliminating the regurgitation, the destructive volume overload effects on the left ventricle are attenuated. The volume overload of mitral regurgitation (MR) relates to the excessive kinetic energy required during isotonic contraction to generate overall stroke volume in an attempt to maintain forward stroke volume and cardiac output. It also relates to the pressure potential energy dissipation of the leaking valve during the most energy-consuming portion of the cardiac cycle, isovolumic contraction. Additionally, successful MR reduction should have the effect of reducing the elevated pressures in the left atrium and pulmonary vasculature reducing pulmonary edema (congestion) and shortness of breath symptomatology. It also has a positive effect on the filling profile of the left ventricle (LV) and the restrictive LV physiology that can result with MR. These pathophysiologic issues indicate the potential benefits of MR therapy, but also indicates the complexity of the system and the need for a therapy to focus beyond the MR level or grade.
It is also desirable to prevent new deleterious physiology or function of the valve. The procedure and system used to fix the mitral valve ideally should avoid worsening other (non-MR) existing pathologic conditions or creating new pathologic conditions as a result of the treatment. One of the critical factors to be managed is mitral stenosis or creation of an inflow gradient. That is, if a valve system is used that does not allow for sufficient LV inflow without elevated filling pressures, then critical benefits of MR reduction are dissipated or lost. Moreover, atrial fibrillation is to be avoided as it can result if elevated pressures are not relieved by the therapy, or are created by the system (high pressure results in atrial stress leading to dilatation ultimately leading to arrhythmias). Also, if the procedure results in damage to atrial tissue at surgery, it can result in the negative physiologic effect of atrial fibrillation. Further, one should be aware of the possibility of increased LV wall stress through an increase in LV size (LV geometry). Due to the integral relationship of the mitral valve with LV geometry through the papillary and chordal apparatus, LV wall stress levels can be directly affected resulting in alterations of LV filling and contraction mechanics. Accordingly, a system that does not preserve or worsens the geometry of the LV can counter the benefits of MR reduction because of the alteration of contractile physiology.
It has been generally agreed that it is preferable if the native valve can be repaired (e.g. with an annular ring), versus an open surgical valve replacement. Repair of valve elements that target the regurgitant jet only results in minimal alteration to the valve elements/structures that are properly functioning allowing for the least potential for negatively affecting the overall physiology while achieving the primary goal. Native valve preservation can be beneficial because a well repaired valve is considered to have a better chance of having long standing durability versus a replacement with an artificial valve that has durability limits. Also, while current surgical artificial valves attempt chord sparing procedures, the LV geometric relationship may be negatively altered if not performed or performed poorly leading to an increase in LV wall stress due to an increase in LV diameter. Thus, while repair is preferred and possible for technically competent surgeons, the relatively high recurrence rate of MR due to inadequate repair, the invasiveness of the surgery especially in sick or functional MR patients, and the complexities of a repair for many surgeons lead to a high percentage of mitral operations being surgical replacement.
Conventionally, surgical repair or replacement of the mitral valve is performed on cardiopulmonary bypass and is usually performed via an open median sternotomy resulting in one of the most invasive high risk cardiac surgical operations performed, especially in subpopulations such as those with functional MR. Therefore, a key improvement to mitral valve operations is to significantly lower the risk and invasiveness, specifically utilizing a percutaneous or minimally invasive technique.
While there have been attempts to replicate existing surgical repair via less invasive surgical or percutaneous methods, given the complexity of repairing the valve surgically, the efforts have largely been deemed lacking in achieving adequate efficacy and have not altered the risk benefit ratio sufficiently to warrant ongoing investment, regulatory approval, or adoption. In particular, there has been a general technology failure due to the complexity of anatomy to percutaneously manage with an implant or implantable procedure. The broad spectrum of mitral disease directly influences outcomes with a resulting inability to match technology with pathology. There has also been observed inadequate efficacy with poor surgical replication and safety results. It has also been recognized that percutaneous approaches have been successful to certain valve procedures, such as aortic valve replacement associated with a single pathology and a relatively circular rigid substrate, mitral valves often suffer from multiple pathologies and a have flexible or elastic annulus with multiple structures, making this a more challenging goal.
Further challenges exist in positioning and orienting mitral regurgitation therapy structures at the interventional site. Cooperation and sealing between component parts has also been a consideration in effective mitral regurgitation therapy. Additionally, more can be done to both identify and take advantage of native anatomical features common to the mitral valve. More can also be done to streamline the implantation process.
Accordingly, what is needed is an effective long lasting MR reduction without creating negative physiologic consequences to the cardio-pulmonary system (heart, lungs, peripheral vasculature) including stenosis, LV wall stress and atrial fibrillation. It is also desirable to be able to perform the operation in a reliable, repeatable, and easy to perform procedure and to have a broadly applicable procedure for both patients and physicians, while employing a significantly less invasive method. Moreover, it is desirable to take advantage of anatomical features leading themselves to an effective mitral regurgitation therapy, and to provide component structures which cooperate to address regurgitation as well as implantation aids facilitating proper orientation and placement.
The present disclosure addresses these and other needs.